cpuset: fix to migrate mm correctly in a corner case
Before moving tasks out of empty cpusets, update_tasks_nodemask() is called, which calls do_migrate_pages(xx, from, to). Then those tasks are moved to an ancestor, and do_migrate_pages() is called again. The first time: from = node_to_be_offlined, to = empty. The second time: from = empty, to = ancestor's nodemask. so looks like no pages will be migrated. Fix this by: - Don't call update_tasks_nodemask() on empty cpusets. - Pass cs->old_mems_allowed to do_migrate_pages(). v4: added comment in cpuset_hotplug_update_tasks() and rephased comment in cpuset_attach(). Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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@ -1563,9 +1563,18 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
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struct cpuset *mems_oldcs = effective_nodemask_cpuset(oldcs);
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mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
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if (is_memory_migrate(cs))
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cpuset_migrate_mm(mm, &mems_oldcs->mems_allowed,
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/*
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* old_mems_allowed is the same with mems_allowed here, except
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* if this task is being moved automatically due to hotplug.
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* In that case @mems_allowed has been updated and is empty,
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* so @old_mems_allowed is the right nodesets that we migrate
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* mm from.
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*/
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if (is_memory_migrate(cs)) {
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cpuset_migrate_mm(mm, &mems_oldcs->old_mems_allowed,
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&cpuset_attach_nodemask_to);
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}
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mmput(mm);
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}
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@ -2152,10 +2161,12 @@ retry:
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/*
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* If sane_behavior flag is set, we need to update tasks' cpumask
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* for empty cpuset to take on ancestor's cpumask.
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* for empty cpuset to take on ancestor's cpumask. Otherwise, don't
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* call update_tasks_cpumask() if the cpuset becomes empty, as
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* the tasks in it will be migrated to an ancestor.
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*/
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if ((sane && cpumask_empty(cs->cpus_allowed)) ||
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!cpumask_empty(&off_cpus))
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(!cpumask_empty(&off_cpus) && !cpumask_empty(cs->cpus_allowed)))
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update_tasks_cpumask(cs, NULL);
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mutex_lock(&callback_mutex);
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@ -2164,10 +2175,12 @@ retry:
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/*
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* If sane_behavior flag is set, we need to update tasks' nodemask
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* for empty cpuset to take on ancestor's nodemask.
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* for empty cpuset to take on ancestor's nodemask. Otherwise, don't
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* call update_tasks_nodemask() if the cpuset becomes empty, as
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* the tasks in it will be migratd to an ancestor.
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*/
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if ((sane && nodes_empty(cs->mems_allowed)) ||
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!nodes_empty(off_mems))
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(!nodes_empty(off_mems) && !nodes_empty(cs->mems_allowed)))
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update_tasks_nodemask(cs, NULL);
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is_empty = cpumask_empty(cs->cpus_allowed) ||
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